It is well known to operate roller doors by means of chain and sprocket mechanisms; however, such systems are not very satisfactory in that they require periodic service, are noisy to operate and require regular lubrication.
It is also well known to control the operation of the roller door or shutter by electrical means, two such electrically operated mechanisms being described in Australian Patent Application Nos. AUA 30718/77 in the name of B. W. N. INDUSTRIES PTY. LTD. and 44163/79 in the name of BYRNE & DAVIDSON DOORS (NSW) PTY. LIMITED. Both mechanisms described in the aforementioned Patent Applications make use of an electric motor having a reduction gear mechanism operatively associated therewith terminating in a pinion which is arranged to mesh with a ring gear to rotate the door curtain in a rolldown or rollup direction. The electric motor in each case is mounted on a movable bracket which can be displaced by actuation of manually operable releasable latch means to a position wherein the pinion no longer meshes with the ring gear whereupon the door curtain may be raised or lowered by hand. With both arrangements, the electric motor and its supporting bracket is mounted externally of and to one side of the curtain drum or rim wheel and as a result, the installation of these control mechanisms require additional room or space. Furthermore, with the electric motor and its associated gear train exposed in this manner, accidental damage may result, for example by a knock or blow, and furthermore the mechanism is likely to accumulate dust and dirt particles which may impede its operation.
It is the main object of the present invention to provide an improved electrically-operated roller shutter or door which requires no additional room or space than is required with the normal installation of a conventional roller door and wherein the likelihood of damage (due to external forces), to the operating mechanism is less likely to occur.
It is a further object of the present invention to provide an improved electrically-operated roller door assembly of improved appearance, of less cost and which is able, in the event of a power failure, to be easily operated by hand.